Vibration isolation systems are utilized in various applications to minimize the transmission of disturbance forces between two bodies or structures. Satellite and other spacecraft, for example, are commonly equipped with vibration isolation systems to reduce the transmission of high frequency vibratory forces or “jitter” emitted from attitude adjustment devices, such as control moment gyroscopes or reaction wheel arrays, to other vibration-sensitive components onboard the spacecraft. The performance of such vibration isolation systems is determined by several factors including the number of isolators within the isolation system, the manner in which the isolators are arranged, and the vibration attenuation characteristics of each individual isolator. Vibration isolation systems employing three parameter isolators, which behave mechanically as a primary spring in parallel with a series-coupled tuning spring and hydraulic damper, generally provide superior attenuation of high frequency vibrations as compared to vibration isolation systems employing other passive isolators, such as viscoelastic isolators. An example of a three parameter isolator is the D-STRUT® isolator developed and commercially marketed by Honeywell, Inc., currently headquartered in Morristown, N.J. Such isolators are usefully implemented as passive, frictionless or near frictionless, single Degree of Freedom (DOF), axially-damping devices utilized within multi-point mounting arrangements.
While capable of providing high performance vibration attenuation without direct reliance upon circuitry or other electronics, existing passive three parameter isolators remain limited in certain respects. During isolator operation, fluctuations in the damping coefficient or “CA” value of a hydraulic damper can occur due to variations in damping fluid temperature and viscosity. In the majority of applications, such variations in damping fluid temperature and viscosity are relatively minor and, therefore, have negligible impact on CA value variation. In specialized applications, however, significant variances in damping fluid temperature and viscosity can occur during isolator operation resulting in undesired CA value variations or changes. This may be the case when, for example, an isolator is deployed within an environment characterized by broad ambient temperature ranges or changes in solar exposure with poor atmospheric shielding; e.g., as may occur in the context of spaceborne and high altitude applications. When sufficiently pronounced, CA value variations can detract from isolator performance, particularly when an isolator is tuned for optimal vibration attenuation over a relatively narrow vibrational band or critical mode of the larger system.
There thus exists an ongoing demand for systems capable of enhancing the performance of hydraulic damper-containing isolators through reduced CA value variation. Ideally, embodiments of such CA-regulating systems would be well-suited for usage in conjunction with passive, single DOF, three parameter isolators having frictionless or near frictionless designs. It would also be desirable if, in at least some embodiments, such CA-regulating systems could be imparted with modular designs facilitating installation onto and removal from selected isolators at any desired juncture following original isolator manufacture. Finally, it would be desirable to provide isolator assemblies containing such CA-regulating systems combined with one or more hydraulic damper-containing isolators. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.